HPLC-MS/MS Determination of Residual Amount of Urotropine in Dried Beancurd Stick

HPLC-MS/MS was applied to the determination of residual amount of urotropine in dried beancurd stick. The sample was extracted with acetonitrile, and fat removed with n-hexane. Kinetex HILIC 100A chromatographic column was used as stationary phase, and the mixture of 10 mmol·L-1 ammonium formate ammonia buffer solution and acetonitrile at different ratios was used as mobile phase in gradient elution. ESI+ and multi-reactions monitor were used in MS/MS. Linear relationship between peak area and mass fraction of urotropine was in the range of 5-100 μg·kg-1, with detection limit (3S/N) of 0.3 μg·kg-1. Recovery measured by standard addition method were in the range of 96.6%-97.5%, with RSD′s (n=6) in the range of 3.9%-7.6%.